Recovery of sulphur from pyrites



Nov.18,1930.

R. F. B ACON RECOVERY OF SULPHUR FROM PYRITES Filed A ril 6, 1927 III I ATTORNEYS Patented Nov. 18, 1930 UNITED STATES RAYMOND F. BACON, OF BRONXVILLE, NEW YORK RECOVERY OF SULPHUR FROM PYRITES Application filed April 6, 1927. Serial No. 181,359.

This invention relates to the recovery of sulphur from iron pyrites, and has for its object the provision of an improved method of recovering sulphur in elemental form from iron pyrites. More particularly, the invention aims to provide an improved method of recovering elemental sulphur from iron pyrites by the action of steam or water vapor at elevated temperatures.

It is known that if iron pyrites be treated with steam at a high temperature most of the sulphur will be removed from the pyrites. The actual chemical reactions taking place are complicated, but the net result is that the sulphur in the pyrites is largely converted into elemental sulphur while some smaller amount is converted into hydrogen sulfide.

So far as I am aware, this process has notbeen commercially used, probably I believe because the amount of superheated steam that is required to effect substantial removal of the sulphur from the iron pyrites is so large that an uneconomical amount of fuel is necessary in carrying out the process.

I have discovered that the sulphur can be removed substantially and completely from iron pyrites at a temperature of about 600 to 700 C. by means of steam and that this-can be done economically by conducting the steam after it has passed over the hot iron pyrites into a condensing apparatus where only a relatively small portion of the steam is condensed to water. Ultimately sulphur separates out in large part in the condensing ap- 36 paratus and the exhaust gases of the condensing operation, consisting largely of steam, are returned to the treatment of further quantities of iron pyrites.

The present invention thus involves sub 40 jecting iron pyrites to the action of steam at Y an elevated temperature, for example, about 600 to 700 (3., and thereby forming a gaseous product containing elemental sulphur and an excess of steam. The gaseous product is then subjected to a condensation operation in which the elemental sulphur is in large part condensed without substantial condensation of the steam. The exhaust gases of the condensation operation are utilized in the further treatment of iron pyrites.

In carrying out the invention, steam is circulated much as in a cyclic operation. Some of the steam is of course consumed by chemical reaction with the iron pyrites, but an excess of steam is always present and constitutes in effect the circulatingmedium. The iron pyrites is confined in an appropriate reaction chamber, such as an externally heated retort, and is appropriately heated to the desired reaction temperature. Steam is then passed over the hot iron pyrites and the resulting gaseous product containing elemental sulphur and an excess of steam is conducted to an appropriate condensing apparatus Where the elemental sulphur is in large part 55 condensed while little, if any, of the excess of steam is condensed to Water. The exhaust gases from the condensing apparatus are then returned to the reaction chamber, or to another reaction chamber containing iron pyrites undergoing similar treatment.

The relatively hot gaseous products resulting from the reaction of the steam and iron pyrites are preferably conducted in heat interchange relation with the relatively cold exhaust gases from the condensing apparatus. A substantial conservation of heat is thereby effected, and at the same time the returning steam is advantageously and economically preheated prior to its introduction 30 into the reaction chamber containing the iron pyrites.

The action of steam on iron pyrites at a temperature of 6007 00 C. is a comparatively complicated one. The net result is that the 35 gaseous product carried over to the condenser is largely elemental sulphur, but contains also some hydrogen sulfide, as well as the excess of steam. In my preferred practice of the invention, I introduce certain propor- The proportion of sulphur dioxide is determined by the hydrogen sulfide content in the gaseous product. The hydrogen sulfide and sulphur dioxide react to form elemental sulphur, and this is precipitated or condensed in the condensing apparatus. This assists in the condensation of the sulphur.

The sulphur may be collected in the con-.

denser in a molten condition, and removed therefrom, from time to time, as desired. Since there there is no condensation of the steam in the condenser, a large excess of steam may be economically used in the treatment of the pyrites. With such a large excess of steam, lower temperatures may be used with satisfactory results.

While the invention is of especial advantage in the treatment of iron pyrites, it is also applicable to the recovery of sulphur from other iron and other metal sulfides. Thus natural iron sulfides of the type of pyrrhotite, and zinc blende, and the like, may be employed in thepractice of the invention. The invention is thus applicable to any metal sulfide whose sulphur content can be in whole or in part removed by reaction with steam at elevated temperatures. Throughout'this specification and the appended claim, I have used iron pyrites as typical and representative of such metal sulfides, and with the intention of including and covering all such metal sulfides, as well as ores, concentrates or other products containing the same.

Various forms of apparatus are available for the practice of the invention. In the accompanying drawing I have illustrated an apparatus satisfactory for the purpose] In the drawing:

Fig. 1 is a diagrammatic view partlyin section of the apparatus, and

.Fig. 2 is a cross-section on the section line 22 of Fig. 1.

The apparatus illustrated in the drawing comprises an inclined cylindrical retort 5 rotatably mounted and operatively connected to a driving motor 6. The retort may be made of any appropriate material adapted to withstand such corrosive influences as result from the reactions taking place between the pyrites and the steam. Iron-nickel-chromium alloys are suitable for the purpose. The retort is enclosed for the greater part of its length in a furnace structure 7, having an opening 8 communicating with a grate or fire box (not shown) and a stack 9. The upper or charging end of the retort extends into a stationary housing 10, and the lower or discharging end extends into a similar housing 11. A feeding hopper andcooperating spout 12 is associated with the housing and is adapted to feed the pyrites into the revolving retort. A residue discharge spout 13 is associated with the housing 11, and is ous products of the reaction between the pyrites and the steam are withdrawn from the retort 5 through an outlet pipe 16 communieating with a heat interchanger 17 and discharging into a condenser 18. The temperature within the condenser is maintained well above the boiling point of water (100 C.) so that no steam is condensed to water. The exhaust gases from the condenser are forced by a pump 19 into the heat interchanger 17 and thence through the heating coil to the supply pipe 14. p

, The condenser 18 has a valved discharge 20 through which the accumulated molten sulphur is withdrawn. The condenser is provided with a coil 21 through which an appropriate cooling fluid may be circulated for the control of the condensation. Sulphur dioxide gas may be introduced into the condenser through the valved pipe 22.

If desired, the exhaust gases, in whole or in part, may be withdrawn from the condenser through the valved pipe line 23 and conducted to another apparatus for the treatment of pyrites. Fresh steam from the steam main 24 may be mixed in any desired proportions with the exhaust gases withdrawn from the condenser and passing to the heat inter changer.

The operation of the apparatus will be understood from the foregoing description. The retort 5 is preferably provided with longitudinal blades 25 which in the rotation of the retort pick up the pyrites and showers the same through the atmosphere of steam filling the retort, thereby securing intimate contact between the pyrites and the steam. The operation is substantially con- C. and not in excess of 700 C. in a rotary retort. subjecting the said heated pyrites while still in the said retort to the action of steam 'at a temperature of about 600 C. and not in excess of 700 (1., thereby forming a gaseous product containing elemental sulphur and hydrogen sulphide together with an excess of' steam, treating. said hot gaseous product with sulphur dioxide at a temperature of about 600 C. and not in excess of 700 C., thereby producing additional elemental sulphur through the reaction of sul hur dioxide with' hydrogen sulphide, subjecting the so treated gaseous product to a condensation operation in which the elemental sulphur is in large part condensed without substantial condensation of the steam, reheating the exhaust gases of the condensation operation by heat de-- rived from the hot gases leaving the retort,

raising the said exhaust gases to a temperature of about 600 C. and not in excess of 700 C. by means of the excess heat from the retort heating device, and reintroducing the reheated ases into the retort for further reaction wit iron pyrites.

- In testimony whereof I afiix m signature.

RAYMOND F. ACON.- 

